In general, a polymer electrolyte fuel cell has a structure in which a plurality of single cells which exert a power generation function are stacked on one another. In usual, each of the single cells includes a membrane electrode assembly having a polymer electrolyte membrane and a pair of electrode catalyst layers which sandwich the polymer electrolyte membrane. Then, the membrane electrode assembly in each of the single cells is electrically connected to a membrane electrode assembly of other single cell, which is adjacent thereto, through a separator. The single cells are stacked on and connected to one another as described above, whereby a fuel cell stack is configured. Then, this fuel cell stack can function as power generation means usable for a variety of purposes.
A brief description is made of a power generation mechanism of the polymer electrolyte fuel cell. At an operation time of the polymer electrolyte fuel cell, fuel gas (for example, hydrogen gas) is supplied to an anode side of the single cell, and oxidant gas (for example, atmosphere or oxygen) is supplied to a cathode side thereof. As a result, individually in an anode and a cathode, there progress electrochemical reactions represented by the following Reaction formula (I) and (II), whereby electricity is generated.H2→2H++2e−  (I)2H++2e−+(½)O2→H2O  (II)
Here, in order to enhance the power generation performance, it is particularly important to enhance catalytic activity in the electrode catalyst layers. Heretofore, as a catalyst in the electrode catalyst layers, a catalyst is disclosed, which includes a particulate underlayer and a platinum layer formed on the underlayer, in which a thickness of the platinum layer is 0.4 nm or more to less than 1 nm (for example, refer to Patent Literature 1).